Apparatus for making threaded concrete pipe.



J. P. ZWICKER.

APPARATUS FOR MAKING THREADED CONCRETE PIPE.

APPLCATIOIN FILED APR.3, 1915.

Patented May 2, 1916.

JULIA POWELL ZWIGKER, OF BERKELEY,

@FICE CALIFORNIA.-

APPARTUS FOR MAKING THREADED CONCRETE PIPE.

Application filed April 3, 1915.

To all whom it may concern.'

Be it known 'that I, JULIA POWELL ZwIcKER, a citizen of the United States, residing at Berkeley, in the county of Alameda and State of California, have invented certain new and useful Improvements in Apparatus for Making Threaded Concrete Pipe, of which the following is a specification.

My invention relates to means for making threaded concrete-pipe. Such pipe, to be serviceable, must have relatively perfect threads, a result attained, in practice, by the use of molds. In such practice, however, several difficulties are found, the principal one of which lies in getting the mold out from the pipe, for, in the nature of things, both with regard to the tight shrinkageI of the setting concrete of the mold, and the fact that the form desired is a pronounced or well defined thread, it follows that the most obvious way in which the mold might be removed, namely, by unscrewing it, is impracticable because it is so tightly bound by the pipe that it cannot be turned out. This difficulty has hitherto been so great that threaded concrete-pipe is rarely made, and, the only solution, in practice, of which I am aware, has been the making of a frangible thread-mold, of plaster-of-Paris or like material which is subsequently broken out. This practice is obviously expensive and troublesome in that it requires a mold for each form to be produced. If a permanent mold could be used, capable of being removed intact, as by unscrewing it, then only two molds would be required, one for the male and one for the female thread.

My invention has this desired result for its object, and this I attain bv the novel apparatus which I shall now fully describe bv reference to the accompanying drawing.

In these drawings-Figure l is a vertical section, broken, of the complete pipe-mold with the concrete filled in. Fig. 2 is a part elevation and part section of the same, showing the application to the thread-molds of the electric heating elements. Fig. 3 shows the completed threaded concrete-pipe, broken in part.

I make two thread-molds, one, indicated by 1, being the mold for the male thread and the other, 2, being the mold for the female thread. These molds are made of some permanent or durable material, best an inflfangble material; one which has, also, a

Specification of Letters Patent.

Patented May 2, 1916. Serial No. 18,915. i

relatively good heat conductivity. In practice, I make them of metal, say, brass, for eaample. When about to use the molds` I dip them in a bath of liquefied material, which will leave upon their surfaces a thin film or coating, which, somewhat exaggerated, is indicated by 3. Theknature of this material must be such that the film or coatmg will be uniform, even and smooth, and sufficiently lubri'cous to avoid sticking to the surfaces with which it comes in contact, and, above all, it must be sufiiciently sensitive to heat to readily fuse or liquefy. I have found that paraffin is best adapted for this purpose. Accordingly, I dip the molds in a bath of melted paraffin, so that a coating or film 3 is left upon their surfaces. Then taking the female-thread mold 2, I lay it down on a base, and I fit to its interior the inside pipe-mold 4, and to its exterior, the outside pipe-mold 5. Then, the concrete C is poured in from above between the pipemolds 4L and 5, nearly to the top. When this is sufficiently settled, I place the male-thread mold l on top, and fill in more concrete to complete the pipe. Finally, I apply heat to the two thread-molds, to a degree sufiicient to melt or reliquefy the paraffin coating or film 3, and thereupon I unscrew said molds from their confining surfaces, said molds leaving the pipeand pipe-molds without any difliculty. Thus the concrete pipe 6, as seen in Fig. 3, with its male thread l and female thread 2 is made.

I may apply the necessary heat to the thread-molds by any suitable means. A very easy and practical way is to make in each mold an annular groove 7, and to insert therein an electric heating element 8, the

current for which is supplied through the circuit wires 9.

The metallic structures of the molds 1 and 2 gives good heat conductivity; and the paraflin film is readily fusible and tends, in melting, to leave the metallic surfaces of the molds and cling in part, at least, to the concrete surfaces, which is no detriment but, in reality, is beneficial, in that it protects the threads and serves to lubricate the union of the pipe sections.

I claim 1. An apparatus for making threaded concrete-pipe comprising concentric, spaced pipe-molds; a male-threadmold applied to one end of the pipe-molds, and a femalethread-mold applied to the other end of said pipe-molds, each of said thread-rnolds having its surfaces Coated With a film or' readily fusible material, and each formed with an annular outwardly opening; groove for the application of a heating medium.

2. In apparatus for making threaded con- Crete-pipe comprising concentric, spaced pipe-molds; a male-threadmold applied to one end of the pipe molds, and a femalethread-mold applied to the other end of said pipeanolds, each of said thread-molds having its surfaces coated with a film of readily fusible material, and each formed with an annular outwardly opening groove; and a heating element for seating in said grooves.

Copies of this patent may be obtained for ve cents each,

by addressing the Commissioner or Patents,

Washington, D. C. 

